JP2012240062A - Die casting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die casting apparatus capable of rapidly solidifying molten metal remaining in a sleeve after injection while suppressing production of small solidified pieces.SOLUTION: The die casting apparatus 100 includes a sleeve 20 for temporarily storing molten metal therein, and a sprue core 30 which is arranged at a sleeve fore end to guide the molten metal to a runner 14 communicating with a cavity. A guide groove 32 for guiding the molten metal to the runner 14 is formed in the sprue core 30. A highly thermal conductive material 34 having the thermal conductivity higher than that of a material of a sprue core section constituting the guide groove 32 is arranged at the front side of the sprue core facing the fore end of a plunger tip.

Description

  The present invention relates to a die casting apparatus.

  Some die casting apparatuses include a sprue core that guides the molten metal to a runner communicating with the cavity at the tip of a sleeve for temporarily storing the molten metal for injection. The sprue core becomes very hot because it is heated by the molten metal. In order to cool the sprue core, for example, Patent Document 1 discloses that a flow path of a cooling liquid is provided inside the sprue core. Patent Document 1 also proposes making a sprue core with beryllium copper as a material having good thermal conductivity.

  On the other hand, after the molten metal in the sleeve is pushed out into the cavity, the lump in which the molten metal remaining between the sprue core and the plunger tip in the sleeve is called a biscuit. Patent Document 2 states that making biscuits quickly (that is, rapidly solidifying molten metal remaining in the sleeve) leads to shortening of the casting cycle time. Cooling the sprue core not only extends the life of the sprue core, but also helps to quickly solidify the molten metal remaining in the sleeve (sleeved residual molten metal).

JP 2010-75939 A JP-A-9-103864

  Keeping the temperature of the sprue core promotes the solidification of the remaining molten metal in the sleeve. On the other hand, if the temperature of the sprue core is low when the molten metal is injected, the melt flowing toward the cavity solidifies as soon as it touches the sprue core. Small solidified pieces that can be carried into the cavity. The present specification provides a die casting apparatus that quickly solidifies a sleeve residual molten metal while suppressing generation of small solidified pieces.

  The die-casting apparatus disclosed in this specification has a high thermal conductivity higher than that of the material of the sprue core portion that forms a groove (guide groove) for guiding the molten metal to the runner on the front surface of the sprue core that faces the tip surface of the plunger tip. It is characterized by arranging materials. Hereinafter, the front surface of the sprue core that faces the tip surface of the plunger tip may be referred to as a “collision surface”. This is because the melt collides with the sprue core front surface at the time of injection. A groove that is formed in the sprue core and guides the molten metal to the runner is referred to as a “guide groove”. Usually, the guide groove is formed at the edge of the front surface of the sprue core.

  The molten metal flow is fast in the guide groove. Therefore, a high heat conductive material is not used for the guide groove, and excessive heat transfer properties are not provided. Thereby, the molten metal is prevented from solidifying while flowing through the guide groove. On the other hand, a high thermal conductive material is provided on the collision surface so that the molten metal in contact with the collision surface can be easily cooled after injection. That is, the time until biscuit formation can be shortened.

  From the viewpoint of securing the strength, the sprue core body including the portion for forming the guide groove is preferably made of an alloy (steel material) containing iron as a main component. As the high thermal conductive material, it is preferable to use an alloy (or pure copper) containing copper as a main component. The thermal conductivity of steel is approximately 20 [W / mK], whereas an alloy mainly composed of copper can ensure a thermal conductivity of 100 [W / mK] or more. The thermal conductivity of SKD61, which is a typical steel material, is about 23 [W / mK]. A typical example of an alloy containing copper as a main component is beryllium copper, and its thermal conductivity is about 200 [W / mK].

  In one aspect of the die casting apparatus disclosed in the present specification, it is preferable that a coating of a substance having a low affinity for the metal of the molten metal is deposited on the collision surface (the surface of the high thermal conductive material). A substance having any of carbon, talc, and boron nitride as a main component is preferable as the substance having a low affinity. These materials have a low affinity for aluminum. These substances are known as mold release agents. In the above die casting apparatus, such a material is not simply applied but deposited. “Precipitating a coating” refers to forming a coating by directly adhering a substance (carbon or the like) deposited from a gas or liquid to a metal surface. For example, when a high heat conductive material is exposed to a gas containing the above substance (carbon) and heated, carbon is precipitated from the gas and is fixed to the high heat conductive material. The coating is thus deposited for example. The coating film is peeled off by the flow of the high-temperature molten metal simply by application, but the deposited film is strongly fixed and difficult to peel off.

  The operation of the coating will be described. By forming a film with a substance having low affinity for the molten metal on the surface of the sprue core collision surface, the adhesion between the molten metal and the coating on the collision surface is lowered and the thermal conductivity is lowered. However, when a high pressure is applied to the molten metal, the adhesion is increased and the thermal conductivity of the coating is increased. From another point of view, when the adhesion between the molten metal and the coating increases, the apparent contact area does not change, but the actual contact area when viewed microscopically increases and the amount of heat transfer increases. It is to increase. Generally, the pressure in the sleeve before the molten metal injection is close to normal pressure and is about 1 [kPa]. On the other hand, in the case of aluminum die casting, the pressure applied to the molten metal after injection is 30 to 80 [MPa]. That is, the pressure of the molten metal has a difference of 10,000 times or more before and after the injection. When such a large pressure is applied, the molten metal is physically pressed against the coating film by the high pressure, the adhesion is improved, and the thermal conductivity is dramatically increased (the adhesion is increased and the amount of heat transfer is increased). That is, if such a coating is formed on the collision surface, until the molten metal injection is completed (until the cavity is filled with the molten metal and the pressure of the molten metal increases), the low adhesion with the coating covering the high thermal conductivity material. Since the thermal conductivity of the collision surface is kept low, the molten metal is difficult to solidify. On the other hand, after the molten metal injection, if the pressure of the sleeve residual molten metal rises to several tens [MPa], the thermal conductivity of the coating increases, the effect of the high thermal conductivity material appears, cooling of the molten molten metal in the sleeve is promoted, and the biscuits are formed. Get early. In other words, a combination of the high thermal conductive material disposed on the collision surface and the low affinity coating on the surface can realize a casting apparatus in which the molten metal cooling ability is low before the molten metal injection and the molten metal cooling capacity is increased after the injection.

  In order to further increase the cooling capability of the sleeve residual molten metal, it is more preferable that a cooling fluid flow path in which the cooling fluid is in direct contact with the back surface of the high thermal conductive material is provided inside the sprue core.

It is typical sectional drawing of a casting apparatus. It is an expanded sectional view near a sprue core. It is a top view of a sprue core. It is a perspective view of a sprue core. It is an expanded sectional view near the sprue core of the biscuit formation drawing.

  First, with reference to FIG. 1, the whole die-casting apparatus 100 of an Example is demonstrated. Hereinafter, the die casting apparatus 100 is simply referred to as a casting apparatus 100. In the figure, only parts necessary for explaining the invention are shown, and some of the parts included in a normal casting apparatus are not shown. The casting apparatus 100 is an apparatus for casting an aluminum molded product. That is, the molten metal of the casting apparatus 100 is aluminum, and the apparatus 100 is an aluminum die casting apparatus. In the casting apparatus 100, the fixed mold 12 and the movable mold 26 constitute a set of molds. When the mold is closed (when the fixed mold 12 and the movable mold 26 are in close contact), a cavity CV, which is a closed space for forming a target product, is formed. The movable mold 26 is brought into close contact with the fixed mold 12 or moved away from the fixed mold 12 by an actuator (not shown).

  A sleeve 20 is attached to the fixed mold 12. The sleeve 20 is a cylinder that temporarily stores the molten metal W before flowing into the cavity CV. The sleeve 20 is sometimes called a sprue bush. The space WS inside the sleeve 20 and the cavity CV communicate with each other through a runner 14 (runner). The runner 14 is a flow path surrounded by the fixed mold 12 and the movable mold 26, and is formed when the mold is closed.

  A plunger 6 is provided inside the sleeve 20 to push out the molten metal. The plunger 6 includes a plunger tip 2 and a rod 4. The plunger 6 is a so-called piston, and the plunger tip 2 corresponds to a piston head. A rod 4 is connected to the rear end of the plunger tip 2, and an actuator (not shown) is connected to the rear end of the rod 4. As the actuator advances / retracts the rod 4, the plunger tip 2 slides in the sleeve.

  A supply port 16 for supplying the molten metal W is provided above the sleeve 20. The molten metal W is supplied from the supply port 16 by the ladle 18.

  When the molten metal W in the sleeve 20 is injected, the molten metal W pushed out by the plunger 6 flows into the runner 14 at a high speed. A sprue core 30 is disposed at a position of the movable mold 26 corresponding to the tip of the sleeve 20 and at a position where the molten metal W flows into the runner 14. The sprue core is also called a “divider” and plays a role of preventing the molten metal W in the sleeve 20 from violently colliding with the movable mold 26 and smoothly guiding the molten metal W in the sleeve 20 to the runner 14.

  Reference numeral 24 in FIG. 1 is a coolant supply / recovery device, and the coolant flows to the sprue core 30 through the flow path 28.

  The sprue core 30 will be described in detail with reference to FIGS. Note that the Z-axis of the coordinate system shown in the figure points vertically upward. 2, 5 and 1 show a cross section including a vertical plane. FIG. 3 shows a plan view of the sprue core 30 as viewed from above, and FIG. 4 shows a perspective view of the sprue core 30.

  The sprue core 30 has a two-stage columnar shape including a columnar base 30 b fitted into the movable mold 26 and a columnar projection 30 a having a smaller diameter than the base 30 b and fitted into the sleeve 20. The top surface of the protrusion 30a corresponds to the collision surface 30c (front surface of the sprue core) that faces the tip surface of the plunger tip 2 when the protrusion 20a is fitted into the sleeve 20. The entire sprue core 30 is made of a steel material SKD61 which is an alloy containing iron as a main component. A copper plate 34 (high thermal conductivity material) is attached to the collision surface 30c. The copper plate 34 is an alloy mainly composed of copper, and is made of beryllium copper, for example.

  As shown in FIGS. 2 to 4, the collision surface 30 c faces the sleeve internal space WS, and a part of the side surface of the base 30 b faces the runner 14. A guide groove 32 is formed from the edge of the collision surface 30 c to the side surface of the base 30 b facing the runner 14. The molten metal W in the sleeve flows into the runner 14 through the guide groove 32 and further reaches the cavity CV. The guide groove 32 corresponds to a flow path for smoothly guiding the molten metal W in the sleeve to the runner 14.

  A carbon coating 36 is formed on the collision surface 30c and the surface of the guide groove 32, that is, the surface in contact with the molten metal. In FIG. 2, the thick lines attached to the collision surface 30 c and the guide groove 32 represent the carbon coating 36. In other figures, illustration of the carbon coating is omitted. The carbon coating 36 is formed by heating the sprue core 30 together with acetylene gas or the like in a nitriding atmosphere to directly deposit carbon in the gas on the sprue core surface. Therefore, unlike the case where the coating is simply applied, the coating 36 is not easily peeled off even when a high-temperature molten metal flows on the surface of the sprue core 30. The carbon coating 36 has a thickness of about 5 to 60 μm. Prior to the formation of the carbon coating 36, the surface of the copper plate 34 is plated with nickel as a base. This is because carbon does not adhere to the surface of copper, but adheres well on nickel. Regarding the method for depositing and forming the carbon coating, refer to Japanese Patent Application No. 2011-045622 and Japanese Patent Application No. 2011-003482 (both are not disclosed at the time of filing this application).

  As shown in FIGS. 1 and 2, a flow path 28 (cooling liquid flow path) through which the cooling liquid flows is provided inside the sprue core 30. As well shown in FIG. 2, the flow path 28 is in contact with the back surface of the copper plate 34. The coolant supplied from the coolant supply / recovery device 24 passes through the flow path 28 and directly contacts the back surface of the copper plate 34 to cool the copper plate 34, and then passes through the flow path 28 to supply the coolant supply / recovery device. Return to 24.

  The advantages of the casting apparatus 100 will be described. The portion of the sprue core 30 forming the guide groove 32 is made of SKD61. On the other hand, a copper plate 34 is attached to the collision surface 30c. The copper plate 34 is exposed to the sleeve inner space WS. The thermal conductivity of the copper plate 34 is much higher than that of the SKD 61. Incidentally, the thermal conductivity of SKD61 is about 23 [W / mK], and the thermal conductivity of beryllium copper is about 200 [W / mK]. Therefore, compared with the collision surface 30c, the molten metal is hardly cooled in the guide groove 32. Further, a carbon film is formed on the surfaces of the guide groove 32 and the collision surface 30c (the surface of the copper plate 34). The carbon film has a low thermal conductivity under normal pressure (about 1 [kPa] a). This is because the molten metal (aluminum) does not adhere to the carbon coating. Therefore, while the molten metal flows through the guide groove 32, the molten metal is not cooled so much and is hard to solidify. Accordingly, solidified pieces are hardly generated. That is, the casting apparatus 100 has a structure in which the solidified pieces are difficult to flow into the cavity.

  On the other hand, after the molten metal in the sleeve 20 is injected into the cavity CV, the residual molten metal in the sleeve is solidified to form biscuits. FIG. 5 shows an enlarged view around the sprue core after molten metal injection. When the molten metal remaining between the sprue core front surface 30c (the surface of the copper plate 34) and the front surface of the plunger 6 (plunger tip 2) is solidified, a biscuit BS is formed. After the molten metal injection, the pressure in the sleeve rises to several tens [MPa]. As a result, the molten aluminum is physically pressed against the carbon coating, the degree of adhesion is increased, and the heat insulating property of the carbon coating is significantly reduced (the thermal conductivity of the carbon coating is significantly increased). Then, the heat of the molten metal is conducted through the copper plate 34 having a high thermal conductivity and further to the coolant flowing on the back surface of the copper plate 34. As a result, the sleeve residual molten metal is rapidly cooled, and biscuits are formed in a short time. The ability to form biscuits in a short time leads to a reduction in casting cycle time.

  As described above, as long as the pressure of the molten metal is low before the injection of the molten metal, the molten metal is not cooled so much, and thus generation of solidified pieces is suppressed. When the molten metal injection is completed and the pressure of the sleeve residual molten metal increases, the thermal conductivity of the collision surface 30c increases, and with the help of the cooling liquid, the residual molten metal in the sleeve is rapidly cooled to generate biscuits.

  The sprue core 30 includes a guide groove 32 that guides the molten metal to the runner 14. As shown in FIG. 2, the guide groove 32 is curved at a substantially right angle. After the molten metal injection, the remaining molten metal remaining in the guide groove 32 is also solidified. The molten metal is solidified along the guide groove 32 while being curved. This curved molten metal solidified portion is connected to the biscuits. When the mold (the fixed mold 12 and the movable mold 26) is opened after the molten metal injection, the curved molten metal solidified portion firmly supports the biscuit, so that the biscuit remains in close contact with the sprue core 30. For this reason, solidification of the sleeve residual molten metal (biscuits) is promoted even when the mold is opened. Since the mold can be opened with the biscuit semi-solidified, the casting cycle time can be further shortened.

  Points to be noted about the casting apparatus 100 will be described. In the embodiment, the coating 36 of the sprue core 30 is a substance mainly composed of carbon. It is more effective if the coating is formed of a material mainly composed of carbon nanofilament or fullerene. Further, instead of carbon, a talc or boron nitride film may be used. The shape of the guide groove is not limited to the above shape.

  The casting apparatus 100 is an aluminum die casting apparatus that uses aluminum for molten metal. The technique disclosed in the present specification can be applied to a die casting apparatus using not only aluminum but also other metals for molten metal.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Plunger tip 4: Rod 6: Plunger 12: Fixed mold 14: Runner 16: Supply port 18: Ladle 20: Sleeve 24: Coolant supply / recovery device 26: Movable mold 28: Coolant flow path 30: Sprue core 30a: Projection 30b: Base 30c: Collision surface (front surface of sprue core)
32: Guide groove 34: Copper plate (high thermal conductivity material)
36: Carbon coating 100: Die casting apparatus CV: Cavity W: Molten metal WS: Space in sleeve

Claims (5)

A sleeve for temporarily storing molten metal,
A plunger for injecting the molten metal in the sleeve into the cavity;
A sprue core that is located at the sleeve tip and guides the melt to the runner leading to the cavity;
With
A die-casting apparatus characterized in that a high thermal conductive material having a higher thermal conductivity than a material of a sprue core portion that forms a groove for guiding molten metal to a runner is disposed on a front surface of a sprue core that faces a tip surface of a plunger tip.   2. The die casting apparatus according to claim 1, wherein a film of a substance having a low affinity for the molten metal is deposited on the surface of the high thermal conductive material.   The die-casting apparatus according to claim 2, wherein the coating is formed of a material mainly containing any one of carbon, talc, and boron nitride.   The sprue core main body including a portion for forming the groove is made of an alloy containing iron as a main component, and the high thermal conductive material is made of an alloy containing copper as a main component. 4. The die casting apparatus according to any one of items 3.   The die casting apparatus according to any one of claims 1 to 4, wherein a cooling fluid flow path is provided inside the sprue core so that the cooling fluid directly contacts the back surface of the high thermal conductive material.

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